Multi-filter devices are well understood in the art. For example, many two-way radios, including cellular telephones, utilize ceramic block duplex filters. Such ceramic block filters typically provide both a transmitter and receiver filter function. The passband for the transmit filter can be, for example, 824-849 MHz in a cellular telephone. The receive passband for a corresponding receiver filter can be 869-894 MHz.
Typically, during the manufacturing process, such ceramic filters must be milled during a coarse tuning process. Many times, this milling process is accomplished through use of a double-sided lap mechanism. When using this process, material is removed from two opposing sides of the ceramic filter simultaneously. This milling process compensates for shifts in the dielectric material itself, and effectively moves the passbands of the filter.
Unfortunately, to date, double-sided lapping techniques will cause both filter passbands in a multi-filter device to be simultaneously changed, but the degree of change in each filter will be different. This can render the coarse tuning process more difficult, and can considerably complicate the fine tuning process that follows.
Accordingly, a need exists for a way to better allow double-sided lapping processes to be utilized when coarse tuning a multi-filter ceramic block.